DEAR DR. BLONZ: With the reports about food poisonings from fruits and vegetables, I wanted to know the best way to clean produce. Is water enough, or should I use something additional, such as a diluted solution of dishwashing liquid (not enough to affect the taste)? -- J.D., Charlotte, N.C.

DEAR J.D.: Fruits and vegetables are not waterproof; unless they have been waxed, they can, to varying degrees, absorb liquids or the components they contain. This means that any fluid you use to wash your vegetables should be approved for food use. Dishwashing detergents, in general, are not. It is important to always clean your produce in potable, running water before eating. This will usually suffice, but if you desire a product that does more, you should seek out one that is specifically designed for washing produce.

DEAR DR. BLONZ: Is there anything to the theory that the healthiest foods are the ones that grow in the area where you live? -- M.S., San Diego

DEAR M.S.: Indigenous foods might be more familiar to our taste buds and to our digestive tracts, but in general, there is no evidence that they possess any special health attributes.

DEAR DR. BLONZ: Is there any unique nutritional value to the Mexican plantano? What is the number of calories in a large, 6-ounce plantano? -- S.Q., Poway, Calif.

DEAR S.Q.: A 6-ounce Mexican plantano, also known as a plantain, contains about 218 calories, along with 2.3 grams of protein, 57 grams of carbohydrate and less than a gram of fat. It is a vegetable, but it looks like large, greenish banana with a mottled, rough peel. Plantains blacken when fully ripe, but can be broiled or sauteed at any degree of ripeness. They are a good source of dietary fiber and vitamin C, along with folate, carotene and potassium.

DEAR DR. BLONZ: What exactly is "palmitate," and why is it in powdered milk? -- N.T. Oakland, Calif.

DEAR N.T.: When you see "palmitate" in the name of a substance, it indicates a compound that is made with palmitic acid, a saturated fatty acid. The name comes from the fact that it is a principle fat found in palm oil. In milk, the vitamin A, or retinol, is combined with palmitic acid; the resulting compound is called either vitamin A palmitate or retinol palmitate. You might also see palmitate in other compounds, such as ascorbyl palmitate, which is a combination of palmitic acid with vitamin C (ascorbic acid).

Interestingly enough, palmitate makes up about 25 percent of the fats found in mother's milk. It's also present in human lung surfactant, a substance that coats the inside of our lung surfaces and allows us to breathe.

The amount of palmitate in powdered milk is negligible. It is only there as an "escort" for the small amount of vitamin A added to the product.

Send questions to: "On Nutrition," Ed Blonz, c/o Universal Uclick, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to questions@blonz.com. Due to the volume of mail, personal replies cannot be provided.

DEAR DR. BLONZ: I was ill recently and I believe it was due to the great amount of stress I was under at work. A friend recommended Rescue Remedy for stress and lack of sleep, but I don't really like taking homeopathic stuff. Have you heard of it? Also, I have been reading the monthly Nutrition Action magazine put out by the Center for Science in the Public Interest (CSPI) for over 20 years, and always feel like I get something out of it, just as I do with your column. My son, who is a molecular biologist, kind of pooh-poohs magazines like this. What do you think? -- T.N.

DEAR T.N.: I am not a supporter of homeopathy. Check out tinyurl.com/mosf6o5 for a recent column on this topic. As for Rescue Remedy, it is my understanding that this product is based on substances referred to as Bach flower remedies. A report in the August 2010 Swiss Medical Weekly presented a systematic review of randomized clinical trials using Bach flower remedies and it concluded there was no difference between the use of the remedies and placebos. As a result there is no basis for me to endorse this product. As for its potential for harm, there is no evidence that it would be harmful, except, perhaps, to one's pocketbook and the delay in addressing the true source of the problem(s).

Regarding CSPI, I have been a member/subscriber to Nutrition Action since they began and consider CSPI to be an important voice. They have an excellent crew of researchers, writers and legal experts and their work represents a positive force. You might also check out the Berkeley Wellness Letter. I am a member of their editorial board and find their evidence-based approach to provide excellent guidance.

DEAR DR. BLONZ: Does beer have a greater diuretic effect than other types of alcohol? When out with friends, I tend to have a couple, but then find myself up multiple times during the night. Would it help to eat salty foods while drinking? -- S.G.

DEAR S.G.: Alcohol affects how much urine the kidneys produce and send into the bladder for elimination. Interestingly enough, it is the amount of alcohol, more so than the amount of fluid, that determines this effect. This means that a shot of liquor, a bottle of beer or a glass of wine can translate to the same diuretic effect.

Your mention of salty foods adds an additional wrinkle. Taking in sodium chloride (salt) tends to increase thirst, since the body is engineered to eliminate excess sodium, but it first has to dilute the sodium to a tolerable concentration. This explains why we cannot satisfy thirst by drinking seawater: It contains a salt concentration above that desired by the body, so any consumption of seawater to satisfy thirst sets the body back even further. You can see where things might head if you then seek to satisfy a salt-bred thirst by consuming alcoholic beverages. Even if you drank plain water, your body would still need to produce urine to get rid of its excess sodium.

Send questions to: "On Nutrition," Ed Blonz, c/o Universal Uclick, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to questions@blonz.com. Due to the volume of mail, personal replies cannot be provided.

DEAR DR. BLONZ: Should I be concerned that there is a great difference in the fishy odor level in the cans of tuna that I open? I'll typically have several cans of solid albacore from the same major brand, but when I open one, it's very smelly, while another identical can will have a very mild odor. Recently I considered throwing out the contents since the fishy odor was so pronounced. Any thoughts on this issue? Any safety concerns? -- F.M., via email

DEAR F.M.: "Solid" types of tuna come from blocks cut from different parts of the fish muscle. They often rely on larger fish for the solid tuna, as the muscle mass will be larger, but this also means you are getting your tuna from an older fish. All, of course, depends on the quality control of the manufacturing process, which includes the tolerances set for what gets included as solid or chunk tuna.

Other possible issues are how the particular cans were processed and stored. If the tuna spent more time in a warmer environment between its time in the ocean and being opened in your home, this could increase the tendency to develop "off" odors that presage the actual breakdown of the tissue and the spoilage process. Fish, especially cold-water fish, have this tendency by virtue of their content of certain fats and amino acids that break down to malodourous substances. All goes well if they remain chilled, but enough time away from the cold, and you have an insult to the senses.

I am of the mind that whenever you crack a can of anything and it has an "off" smell, you should not eat it. You have the option of contacting customer support at the manufacturer and telling them your story (there should be contact information on the tin). Likely they will also tell you to toss the stuff (they might ask for the lot identifiers first), and I would predict they will send you some coupons for a replacement product. Another option is to take it back to the store where you bought it and get your replacement can that way.

As long as we are talking about tuna, you should be alert to the issue of mercury. Albacore tends to have higher levels of mercury than chunk light, which usually comes from skipjack -- a smaller-sized, shorter-lifespan breed. Tuna tend to bio-accumulate mercury and the older the tuna, the greater the risk.

The main reason for this is that albacore tend to live longer and are moderately large among the breeds used for canned tuna. As such, bigger albacore caught for large commercial canners tend to come from deep waters and will have a higher risk of mercury. There are brands, such as Wild Planet (wildplanetfoods.com), that catch younger, smaller tuna. Their fishing methods include pole-and-line or trolling, and those result in fish with a lower risk of mercury. You can do some additional research at tinyurl.com/d464hdm before you buy.

Send questions to: "On Nutrition," Ed Blonz, c/o Universal Uclick, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to questions@blonz.com. Due to the volume of mail, personal replies cannot be provided.